Re: [HACKERS] best way to determine start of new statement within
The semantics of this conceptually is not too bad. The implementation could be tricky. For any given DML or sub-DML (select, eg) the scope should be for that DML. The DML is the parent of the function. The DML is the statement context and the function is the function context. statement -- function | + -- statement -- function | + -- statement statement -- function1, function2 | | | +-- statement - function3 | | | +-- statement | | | + -- statement -- function4 | + -- statement For example: select myfunc() from foo; -- 1 statement select myfunc() from (select myfunc2() from foo); -- subselect ( select ): both actually have the same memory duration, but have different statement contexts and different function contexts. -- the scope of each matches its select select myfunc() from foo; --where myfunc invokes select myfunc2() from bar; The scope of myfunc is the parent select. The scope of myfunc2 resets at each iteration of myfunc(), but is available for each iteration of itself. Note that these things can nest very deeply. select myfunc() from foo where myfunc3() = 't'; -- both myfunc() and myfunc3() have the same statement parent. -- if myfunc3() invoked select * from myfunc4() then each iteration of myfunc3() resets the statement context of that select. The new statement corresponds to a single invocation of one DML. Memory should last through the whole invocation loop. Am I making sense here? Where does the function context info memory get available for allocation and where does it get deallocated? (It does get deallocated via garbage collection, right?) I think the scope of this is correct. We implemented this at informix and got a lot of stuff wrong. Memory pool hell, but we had to deal with a multi-threaded server. Illustra did it right so I think postgres already has the handles to the hook the memory into the right scope. Do you want me to try to write this up into more formal definitions? elein On Fri, Jul 25, 2003 at 08:31:14AM -0700, Joe Conway wrote: Tom Lane wrote: Joe Conway [EMAIL PROTECTED] writes: Specifically I'd like to reset a variable within my PL/R interpreter each time a new SQL statement begins. Define new SQL statement. In particular, what of a PL function executing multiple SQL statements inside an outer SQL statement that invoked the function? Unless you've got a clear idea of the semantics you want, it's not going to be very profitable to discuss implementations ... Well, I guess in a situation like this: a) SELECT * FROM myfunc1()... where myfunc1() executes via spi b) SELECT * FROM myfunc2()... I'd be interested in being able to detect when outer statement (a) starts, as well as the fact that it is at nesting level 0. And similarly it would be nice to be able to detect when statement (b) starts along with the fact that it is at nesting level 1. But for the moment, I'd be happy with just the former. Joe ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] best way to determine start of new statement within a function? (resend)
I was starting to wonder if my message got there. Tom had asked for a clear definition of what is a statement hence the wide description. If I wrote this up more formally where would I put it so we could talk about it when the various issues come up? Maybe a friend-of-the-court unapproved functional spec in the dev docs? Noting, of course, that this is functional not implementation specifications. I'm surprised these issues did not come up with who ever is working on nested transactions since that is in the same realm. elein On Mon, Jul 28, 2003 at 09:58:42AM -0700, Joe Conway wrote: elein wrote: Do you want me to try to write this up into more formal definitions? I think it would be a useful starting point for future discussions, but it goes way beyond what I was looking for at the moment. Joe ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [HACKERS] best way to determine start of new statement within
elein wrote: Do you want me to try to write this up into more formal definitions? I think it would be a useful starting point for future discussions, but it goes way beyond what I was looking for at the moment. Joe ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [HACKERS] best way to determine start of new statement within
Tom Lane wrote: Joe Conway [EMAIL PROTECTED] writes: Specifically I'd like to reset a variable within my PL/R interpreter each time a new SQL statement begins. Define new SQL statement. In particular, what of a PL function executing multiple SQL statements inside an outer SQL statement that invoked the function? Unless you've got a clear idea of the semantics you want, it's not going to be very profitable to discuss implementations ... Well, I guess in a situation like this: a) SELECT * FROM myfunc1()... where myfunc1() executes via spi b) SELECT * FROM myfunc2()... I'd be interested in being able to detect when outer statement (a) starts, as well as the fact that it is at nesting level 0. And similarly it would be nice to be able to detect when statement (b) starts along with the fact that it is at nesting level 1. But for the moment, I'd be happy with just the former. Joe ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] best way to determine start of new statement within a function? (resend)
The semantics of this conceptually is not too bad. The implementation could be tricky. For any given DML or sub-DML (select, eg) the scope should be for that DML. The DML is the parent of the function. The DML is the statement context and the function is the function context. statement -- function | + -- statement -- function | + -- statement statement -- function1, function2 | | | +-- statement - function3 || |+-- statement | | | + -- statement -- function4 | + -- statement For example: select myfunc() from foo; -- 1 statement select myfunc() from (select myfunc2() from foo); -- subselect ( select ): both actually have the same memory duration, but have different statement contexts and different function contexts. -- the scope of each matches its select select myfunc() from foo; --where myfunc invokes select myfunc2() from bar; The scope of myfunc is the parent select. The scope of myfunc2 resets at each iteration of myfunc(), but is available for each iteration of itself. Note that these things can nest very deeply. select myfunc() from foo where myfunc3() = 't'; -- both myfunc() and myfunc3() have the same statement parent. -- if myfunc3() invoked select * from myfunc4() then each iteration of myfunc3() resets the statement context of that select. The new statement corresponds to a single invocation of one DML. Memory should last through the whole invocation loop. Am I making sense here? Where does the function context info memory get available for allocation and where does it get deallocated? (It does get deallocated via garbage collection, right?) I think the scope of this is correct. We implemented this at informix and got a lot of stuff wrong. Memory pool hell, but we had to deal with a multi-threaded server. Illustra did it right so I think postgres already has the handles to the hook the memory into the right scope. Do you want me to try to write this up into more formal definitions? elein On Fri, Jul 25, 2003 at 12:53:11AM -0400, Tom Lane wrote: Joe Conway [EMAIL PROTECTED] writes: Specifically I'd like to reset a variable within my PL/R interpreter each time a new SQL statement begins. Define new SQL statement. In particular, what of a PL function executing multiple SQL statements inside an outer SQL statement that invoked the function? Unless you've got a clear idea of the semantics you want, it's not going to be very profitable to discuss implementations ... regards, tom lane ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
[HACKERS] best way to determine start of new statement within a function?
I know that I can use fcinfo-flinfo-fn_extra to determine if a particular function has been previously called within a given SQL statement execution, but what is the best way to determine that the current statement has or has not changed? Specifically I'd like to reset a variable within my PL/R interpreter each time a new SQL statement begins. Joe ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] best way to determine start of new statement within a function?
Joe Conway [EMAIL PROTECTED] writes: Specifically I'd like to reset a variable within my PL/R interpreter each time a new SQL statement begins. Define new SQL statement. In particular, what of a PL function executing multiple SQL statements inside an outer SQL statement that invoked the function? Unless you've got a clear idea of the semantics you want, it's not going to be very profitable to discuss implementations ... regards, tom lane ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
